The Difference Between Continuous Integration, Continuous Delivery, And Continuous Deployment

Few things are more confusing than vague tech-related jargon. When it comes to DevOps, the phrases Continuous Integration, Continuous Delivery, and Continuous Deployment might well take the cake. It might well be easy to get these similar ideas confused with one another, given some of the basic definitions for each floating around…

Continuous Integration basically just means that the developer’s working copies are synchronized with a shared mainline several times a day.

Continuous Delivery is described as the logical evolution of continuous integration: Always be able to put a product into production.

Continuous Deployment is described as the logical next step after continuous delivery: Automatically deploy the product into production whenever it passes QA.

Nebulous descriptions like that make it easy to think the degree of separation between these concepts is inconsequential. Those subtle distinctions make knowing the differences worthwhile, however. In this post, we’re going to cover the meanings of these terms in greater detail, along with what makes each unique and how their variances matter.

Continuous Integration

When practicing Continuous Integration, developers will frequently merge their changes back into the main branch of a shared cache. Instead of building separate features in isolation and incorporating those individual changes into software at the end of a development cycle, multiple developers will integrate their code to the mainline several times throughout their day (under ideal circumstances).

Using a build server specifically designed for automated testing, the changes are put through their paces to catch potential conflicts early on, avoiding the so-called “integration hell” that might occur when attempting to integrate changes mere days before a product is due to release.

Circumventing a situation where software might work on an individual developer’s machine but fails when combined with the code from other developers who are working on different parts of the same project is a boon in and of itself. The benefits, however, go beyond that.

Using a strategy of Continuous Integration can also boost the productivity of individual developers. As they produce code, it is integrated and tested with other developer’s code. By gaining immediate feedback on code and integration errors, they can respond to problems quickly, making necessary corrections before they become larger issues and keeping them in a near-continuous state of progress.

These potential benefits, however, are only a net positive when combined with a degree of automation, however. Simply integrating code does not guarantee a superior product. Those changes must be tested to ensure proper functionality. When organizations use manual methods to ascertain if new code is introducing bugs, tampering with operations, and, in general, is up to standards, Continuous Integration can put a strain on time and resources.

By making use of automation and test suites, the process becomes much more feasible. Instead of manually running the required tests, developers can upload code, then automated processes will handle creating a new software build and testing it for integration errors. Should any problems arise, the dev team will be alerted, allowing them to move swiftly to correct complications before proceeding.

In the end, the idea is to make integration a simple, routine process rather than a nightmare that occurs near the end of a development cycle. The team has the ability to correct programming defects early on, and the overall costs of integration are, as a result, reduced.

Continuous Delivery

As the “logical extension of Continuous Integration,” Continuous Delivery incorporates much of the same in its process. The development team is still making and testing frequent changes to the software they are working on, but a new wrinkle is added into the scheme: the software delivery process is also automated, so that dev teams are ready to get their code to production at a moment’s notice.

Like Continuous Integration, Continuous Delivery relies heavily on automation to ensure it works correctly. You may have well heard of the concept of a deployment pipeline before. It’s the creation of an automated process to get software from version control phases into the hands of users. This additional step is added to the frequent integration and testing of Continuous Integration, so that developers can get their software out quickly while making changes — should they choose to do so.

That last point is important, because having the option to deploy while they work on upgrading software in smaller chunks is of great benefit to development teams. It allows them to focus and gain feedback on their work more often while simultaneously being able to deliver new features and functionality to their customer base when they are ready. The process also benefits those end users, as they reap the rewards of these changes on a much faster basis.

In traditional “waterfall” methods of development, users of a piece of software could wait months before seeing the fruits of developers’ changes to code. With Continuous Delivery, the process could potentially be cut to days or even hours. Users can provide feedback to a development team on what a product could be lacking and where it might be improved. The developers, in turn, can use a Continuous Delivery scheme to rapidly update and bring such changes to their user base.

The result is a demystification of the software release cycle. Instead of a much ballyhooed affair, it becomes a routine and rather rote procedure, instilling the dev team with greater confidence that they have a quality product, and letting customers enjoy that higher quality product faster than they might have via other methods.

Continuous Deployment

Continuous Deployment has a lot in common with Continuous Delivery. Both processes build on the Continuous Integration idea of frequently weaving and testing code to ensure its ready to go. Both operate on the idea of having product code ready to send to customers as swiftly as possible. Where Continuous Deployment differs from Continuous Delivery, however, is in the fact that software builds are deployed automatically after they undergo testing.

This setup does away with the need for the human decision making that would otherwise go into whether or not to get new, fully tested code out to users, thereby further enhancing the speed of the rollout. It’s important to bear in mind, however, that just because these new software iterations are automatically deployed, that doesn’t mean they are instantaneously activated. Developers can still employ techniques to control when new features become live and which segments of users gain access to them if need be.

Continuous Deployment comes with many of the same benefits that Continuous Delivery does. Dev teams can gain from and respond to user feedback in a rapid manner. This allows them to course correct if they are heading in a sub-optimal direction with a product, and get the software back on track so that it meets user standards. Beyond that, though, the automation of the deployment of software changes to customers reduces confusion over what’s going to the user base and enhances productivity by allowing devs to focus on ever smaller facets of their software.

There is risk, of course, in such a high degree of automation. The seeming lack of control can cause anxiety for some developers who might want to have the final say on when software is pushed out to their users. On the flip side, though, the Continuous Deployment method puts an even greater onus on developers to ensure they follow best practices and maintain that they’re code is well-written, well-tested, and worthy of production on a consistent basis.

Bringing It All Together

Though each methodology differs slightly in nature, there are overarching themes that bind them together. In all three of these software approaches, the emphasis is on speed and manageability. Code is developed in smaller waves to minimize the possibility of integration issues and reduce the time it takes to test for errors. Testing must be performed frequently to ensure that the team is ready to jump to production, and it must all occur daily to keep the development cycle running smoothly.

In spite of the small distinctions between the three individual methods, when done correctly, they help reduce production times and make it so that integration and software deployment goes a swiftly and smoothly as possible.